Partial stringent control of polymer synthesis, caused by partial amino acid deprivation, initiates bacterial sporulation. It is accompanied by increase of ppGpp and decrease of GTP. This was shown under step-down conditions from rich media and in auxotrophs deficient in active amino acid transport. Certain antibiotics prevent sporulation because they interfere with this stringent control. All studies showed that a decrease of GTP is associated with the initiation of sporulation. To determine the mechanism of GTP, RNase and enzyme synthesis, membrane synthesis and transport, and cell wall synthesis were studied. A continuously sporulating strain was genetically and biochemically analyzed and shown to be partially deficient in pyruvate carboxylase. The special need of branched chain fatty acids for growth and sporulation was also examined.